Coastal floodwater covering a patio: white chairs and a picnic table stand in moving brown water up to their seats, with a submerged dock, a half-buried fence, and the far shoreline behind them.
Coastal Flood Alerts for iOS

Know before the flood
reaches you

Real-time NOAA water level monitoring with flood alerts for your coast.

Download on the App Store

Free download · optional CoastWarn Pro lifetime unlock, $19.99 one time

Features

Built on official data. Designed for peace of mind.

Real-Time Water Levels

Live data from 48+ NOAA CO-OPS tide stations across the U.S. coastline, updated continuously.

Official Flood Thresholds

Uses National Weather Service flood stages — minor, moderate, and major — not arbitrary guesses.

Instant Alerts

Get alerted the moment water levels exceed your threshold. No need to keep the app open.

Nationwide Coverage

East Coast, Gulf Coast, West Coast, Alaska, and Hawaii. If NOAA monitors it, CoastWarn covers it.

Free to Start

Download free and monitor your station. Unlock CoastWarn Pro with a one-time $19.99 purchase — no subscription, yours for life.

How It Works

Three steps to coastal peace of mind

1

Enter your zip code

Tell us where you are. We'll find the nearest NOAA tide station automatically.

2

We find your station

CoastWarn matches you with the closest monitored station and its official NWS flood thresholds.

3

Get alerts

When water levels cross your threshold, you get a notification on your iPhone. That's it.

Powered by NOAA CO-OPS
real-time water level data

CoastWarn is not a substitute for official National Weather Service warnings. Always monitor official sources and follow local emergency management guidance.